With the continuous development of communication technology, a full range of service requirements of users need to be met by operators. It can be seen from the integration of telecommunication networks, broadcast television networks and mobile network, there is a general trend to enable the operators to have a capability of all-service operation through the integration of a variety of services. This requires that a communication network must support a variety of services, however, various services have different Quality of Service (QOS) requirements. QOS refers to a series of service requests required to be met by a network when a data stream is transmitted in the network and a mechanism for implementing these service requests. These service requests may be evaluated by a series of indexes, for example, a bandwidth requirement, a transmission delay, a jitter, a packet loss rate, a throughput, etc.
The communication network generally implements the QOS requirements of the network using a traffic management chip. At present, there are two scheduling mechanisms used for traffic management, i.e., a data push scheduling mechanism and a pull scheduling structure, wherein, the data push scheduling mechanism performs corresponding scheduling only after a traffic message arrives at a scheduling node. This scheduling structure is generally divided into two scheduling, i.e., scheduling at an input side and scheduling at an output side. The disadvantages thereof are as follows: there is a physical queue in each level, a lot of queue memories are required, and the requirements on the bandwidth of the control memory and the processing capability of the circuit are high. With the continuous increase of the network capacity and services, the use of such scheduling structure will enable the memories of the traffic management chip to increase exponentially, which limits the number of traffics managed by the chip and is disadvantage to the subsequent expansion.
The feature of the pull scheduling structure is that the actions of the scheduler is driven by authorization, and may not be processed in real time, and there is a low requirements on the bandwidth of the memory controller or the processing capability of the circuit. In a Chinese Patent with a patent application No. 201010236242.2 entitled “TRAFFIC SCHEDULING DEVICE AND METHOD IN A PACKET SWITCHED NETWORK”, the pull scheduling is described in detail. The patent specifically discloses that the whole authorization surplus of all queues is maintained in real time, and when the whole authorization surplus is greater than a preset threshold, the authorization representing a fixed number of bytes is transmitted to the queues waiting for authorization, and the queue management module transmits the data packets in the queues in the waiting queues.
The key point of the pull scheduling structure is authorization and management, but the pull scheduling method disclosed in the above patent does not manage the authorization surplus well, and the jitter is poor after the traffic scheduling of queues. The reason is that the whole authorization surplus of all queues is maintained, and the authorization is generated according to a fixed size of granularity, however, the length of the data packet of each queue is different. For example, some queues are long packets in a period of time, after the packets are transmitted, it will cause the whole authorization surplus become negative, as a result, some queues transmit packets, but some other queues can transmit packets only after the whole authorization surplus becomes positive. This results in jitter in the traffic of some queues.
Therefore, there is an urgent need to propose an improved pull scheduling method, which can better control transmission of authorization, and effectively reduce message jitter after traffic scheduling of queues.